Wow,
Got a lot of feedback with some questions that I can answer to fill in a few
gaps of my earlier posting- seems like I left a lot of details out-
First, the top hat wires are at a 45 degree angle downward- they are at
about the same angle as the guy ropes-
As for raised radials- ON4UN really goes into detail on his single rasied
radial system per vertical on his 80 meter four square- I researched this a
lot and found a variety of opinions on how effective they are or may not be
compared to ground radials- ..... the findings seemed to indicate that the
higher the raisied radials, the better. But that is another topic for
someone other than me - I feel like those three monkeys talking about the
subject- I see no, hear no, speak no on raised radials- hihi
But before building the array, I emailed every one of the four square owners
listed in ON4UN 3rd edition of world renowned DX'ers what kind of radial
system they used...the vast majority used ground radials- some tried using a
single raised radial over a good ground screen with decent results- But
after all my time investigating things, I just wanted to keep it simple and
not screw around with the potential for interaction between the rasied
radials that parallelled one another etc..... -
Why 60 radials??? well, 30 radials are nice, but if your going to do it, 60
really improves things while going from 60 to 120, per other's research, is
not as significant- so 60 seemed like a good number to settle on and is what
Com Tek suggested- many 4 sqr owners agreed that 60 seemed to be the magic
number- I cut them at 1/4 wave lengths to keep them uniformed from antenna
to antenna-
The distance of one wave length to buffer the antenna radial tips from other
potential effects is my own paranoia- but it sounds good and makes me feel
intelligent- although the dictionary states that is a sign of
insanity...........Har!
Actually, I do have a beverage running near by the tips of some of the
raidals- and a few of the radials tips of my 160 Inv L actually come into the
radial field by a few feet- but none criss cross the 80 meter radials- and no
ill effects have been noticed- yet.......
Mutual coupling has been a big subject- Like a few of you responding, I too
thought that the jump in resonance was a result of the 4 verticals being
coupled through the hybred coupler- but not true-- Charlie, W0YG,
straightened me out on this-
He explained that the resonant point jump from where I first tuned the
original vertical, standing alone, with no other verticals in the field,
because of the mutual effect of the four vertical's proximity standing near
one another.
To prove this, he had me disconnect all the feedlines from the hybred
coupler to the verticals and test out each vertical by itself- and you know
what, the results were the same resonant point for each vertical as it was
for the array- Each vertical showed a resonant point near 3.900MHz......the
same frequency that showed the minimal power dumped into the dummy load with
the array hooked up- thus, the most resonant point of the array agreed with
what seemed to be the resonant point of each individual antenna- -
I'm sure the hybred coupler has some minimal effect, but the main factor
influencing the "jump" is due to mutual coupling of the antennas...it is a
neat effect and one you may never see until you start working with
array's.....
And as for the "cheap feedline" I use to run back from the power dump port to
the dummy load.......the coax run is around 400 feet- the coax runs from the
array back into my shack where it is hooked up to the watt meter and then
the dummy load- it is all RG8 and/or 9913- it is not RG59....I guess
referred to by many as the cheap stuff-
The verticals are ground mounted. They sit on 2 1/2 inch PVC, the gray type
(the white stuff is too light) The PVC is 3 feet long with about 2 feet 3
inches of it sitting in concrete. I roatated the PVC during curing and it
allows me to pull it out of the concrete if I need to- More importantly, it
allows me to slighttly rotate the antenna to match it up with concrete
guyline supports about 45 feet from the base of the antenna-
The base of each vertical is about 8 inches off the ground- I have the
ground braid attached to the radials via a ground bus and the center
conductor is attached about 1 inch from the base of the aluminum- I'm
planning to use hay bails and plastic bucket to shield the feedpoints from
snow drifts later this year-
The coupler is mounted in the center of the square formed by the verticals-
it is attached to a 6 inch diameter log post in 4 bags of concrete- The
center support was important as I use it for atttaching guy ropes to-
overkill??? maybe- but we get steady winds here in SE Wyoming- and the
winter winds are really a pain-
I used conductive grease to insure good contacts between to aluminum sections
and put in two screws to hold them in place and a metal O ring to squeeze
them together-
I used the 0 ring connectors to attach the guy wires and top hats too- Care
was given so as not to cut into the wire or guy ropes- with minimal loading
in the wind, I dont foresee a problem- (famous last words.......)
I did seal the tips of the verticals using electrical tape and silicon-
Have I nicked named it yet??? Yes, my XYL calls it the Big-A-Lou because of
all the aluminum we put into it- the Big A Lou 4 square by N0AH......has a
ring to it- but after spending a month building it- I don't see a product
line anytime soon- hihi
And my favorite question was more of a comment on forgeting to add to the
cost of the antenna the $$$ for the two acres it takes up- $800 bucks-
really! But thats SE Wyoming for you- I guess folks in San Fransisco or
downtown NYC might consider other options to use 2 acres of land for but I
can't think of anything better- (-:
phew- thats it for the first night of questions/comments- I was amazed by
the number of e-mails I got- I guess I forgot a few things- really nice to
get the feedback- -
73 Paul N0AH
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